The purpose of the surgical drape is to place a bacteria barrier between the aseptic operative field and areas which are incapable of surgical cleansing. The drape also provides the physician while working on the patient, a sterile area on which to lay surgical instruments and the like. The drape should be sufficiently flexible or drapable so that it may somewhat conform to the contour of the body which it is covering, and so that it may hang down over the edges of the operating table without interfering with the physician's work. The drape should be absorbent so that it may collect exudate from the operative site and should also provide enough friction so that the drape does not slide off the patient during the operation.
Microfine fiber fabrics (preferably produced by melt blowing) are useful in surgical drapes, as repellants or impervious bacterial barriers. Due to a variety of end-user needs, it is desirable at times to have a more textile-like surface or an absorbent fabric surface on this impervious structure. To accomplish this objective, lamination techniques involving adhesives or thermal bonding can be employed, but they can present problems in rupturing the fabric or interfering with some other aspect of the product functionality due to the inclusion of adhesives. The present invention, as described hereinafter, overcomes these problems.
Certain disposable drapes are known which consist of nonwoven mats of heat fusible fibers fused to one or both sides of nonwoven fabrics comprising multiple plies of microfine fibers. However, in producing this type of fabric, the heat fusible fibers are fused so that the integrity of the fibers is destroyed. The present invention provides a multiple ply hydrophobic microfine fiber structure which is preferably area fuse bonded on at least one side to a layer of conjugate fibers having a low melting sheath and a high melting core. The sheaths of the conjugate fibers are fuse bonded to the hydrophobic microfine fiber structure at a temperature below the melt temperature of the cores of the conjugate fibers so that the cores retain their initial fiber-like integrity. A preferred embodiment of the present invention comprises a three-ply hydrophobic microfine fiber structure sandwiched between and preferably area fuse bonded to two layers of conjugate fibers. The inner ply of the hydrophobic microfine fiber structure is relatively high melting while the two outer plies of the hydrophobic microfine fiber structure are low melting, the melt temperature of the outer plies of the hydrophobic microfine fiber structure being close to the melt temperature of the conjugate fiber sheaths, so that excellent fusion takes place when these conjugate fiber sheaths and the outer plies of the hydrophobic microfine fiber structure are bonded together or emboss bonded. In addition, the inner core of the three-ply hydrophobic microfine fiber structure is not fused during the bonding procedure and this prevents any large perforations being formed in the hydrophobic microfine fiber structure during emboss bonding. Thus, there is no interruption of the impervious nature of the total structure.
The laminate of the present invention is useful not only for surgical drapes but also in the areas of filter media such as surgical face masks. In this connection, the bulky microfine fiber core provides the tortuous path for bacterial filtration and the microfine fiber components on the surface of the hydrophobic microfine fiber structure provides good bonding or lamination with the surface veneer of conjugate fibers required for strength and abrasion resistance of the total structure. This combination enhances the fabrication of the resultant product through the elimination of slippage and buckling between the multiple plies and at the same time ensures better performance through molding operations where there would be uniform stretch distribution in the total composite rather than a tendency to fracture the microfine fiber core.
The expression "area fuse bonding," between two contacting surface, as used herein, means that fuse bonding takes place over the entire area of the contacting surfaces.
The microfine fibers utilized in the present invention are preferably produced by melt blowing. However, microfine fibers can also be produced, for instance, by a centrifugal spinning operation (see Vinicki's U.S. Pat. No. 3,388,194).